Chipotle Mexican Grill just gave Wall Street a bad case of indigestion.

Shares of the Denver-based fast-food chain took their worst-ever single-day hit after unexpectedly sluggish demand for the company’s tacos, burritos and salads caught investors off-guard.

“We’re seeing a slowdown — I mean, there is no other way around it,” Chief Financial Officer Jack Hartung said on a conference call late Thursday. “It’s a very fairly sudden trend, and it’s still a trend that we’re trying to figure out.”

While Chipotle execs blamed a recent fall-off in consumer spending, stiff competition and difficult comparisons with last year’s torrid growth were also possible culprits, execs said.

Chipotle’s stock — which, according to some analysts, had been priced as if the chain’s speedy growth would continue indefinitely — plunged $86.88, or 21.5 percent, to close at $316.98.

Shares of other fast-food chains including McDonald’s, Starbucks and Panera also fell on fears that consumers, concerned about unemployment and a wobbly economy, are cutting back on restaurant visits.

Compared with other fast-food chains, Chipotle’s second-quarter results were a picture of health.

Net income surged 61 percent as sales at restaurants open at least a year — a closely watched measure known as comparable sales — rose 8 percent.

That disappointed investors who had been expecting comparable sales growth of at least 10 percent. Chipotle, which went public in 2005, saw its shares sink to their lowest levels since 2009.

“The balloon has now popped,” said Raymond James analyst Bryan Elliott. “This stock reached cult status, and the market just got ahead of reality.”

Lukewarm sales growth at McDonald’s in May was one of several warning signs that consumers have begun to eat out less, Elliott said.

While lower-income diners have been pummeled by tepid job growth and stagnant real wages, Elliott said upper-middle-income consumers are uncertain about the presidential election and the stock market.